This invention relates to a waterproof/oilproof electromagnetic shielding structure used at a portion where electric wires (cables) are connected respectively to input/output terminals of a motor of an electric car or an ordinary electronic/electric equipment.
Recently, small current circuits and electronic circuits have increasingly been used in automobiles, and installed wires have now had a large-current/high-voltage design, and under these circumstances, it has been required to provide effective and inexpensive electromagnetic shielding measures which protect the small current circuits liable to be affected by electromagnetic noises, and will not lower the detection precision of various sensors in the electronic circuits under the influence of electromagnetic noises.
In a related electromagnetic shielding structure, a plurality of pin terminals 3 are held by a terminal-holding retainer 2 provided within a cylindrical metal shell 1, as shown in FIG. 14 which is a side cross-sectional view. A shielded cable 4, shown in FIG. 14, comprises a plurality of twisted insulated core wires 5 each having a conductor 5a covered with an insulator 5b, a metal braid 6 wound on the twisted core wires 5, and an outermost sheath 7 covering this metal braid. The insulator is removed from an end portion of each insulated core wire 5 of the shielded cable 4, and the exposed conductors 5a of the core wires 5 are connected to the pin terminals 3, respectively.
The sheath 7 is removed from an end portion of the cable, thereby exposing the braid 6, and a tubular metal net 8 is fitted on a skirt-like end portion of the braid 6, and further a heat-shrinkable tube 9 is fitted on the metal net 8. The heat-shrinkable tube 9 is heated to tighten the metal net 8 by its shrinking pressure, so that the metal net 8 is pressed against an outer peripheral surface of the metal shell 1, and therefore is connected thereto, thereby electrically connecting the braid 6 to the metal shell 1, thus achieving an electromagnetic shielding effect (see, for example, JP-UM-A-6-23179 (Page 2, FIG. 1)).
One known electric connector, employing an electromagnetic shielding structure different from the above electromagnetic shielding structure, is shown in FIG. 15 although such an electric connector is not clearly disclosed in any technical literature. Namely, in this case, a shielded wire (or shielded cable) 20 includes an insulator 22 covering a conductor 21, an outermost sheath 23 covering the insulator 22. A braid 24, serving as a shielding layer, is embedded between the inner and outer layers, that is, the insulator 22 and the sheath 23, and generated electromagnetic waves are absorbed by the braid 24. A metal terminal 25 is press-fastened to the conductor 21 at a distal end of the wire, and this metal terminal 25 is connected to an input/output terminal of an equipment.
In this case, the sheath 23 is removed from the distal end portion of the shielded wire 20, thereby exposing the braid 24 and the insulator 22 (which are disposed within this sheath), and an end portion of the exposed braid 24 is connected to a metal collar 26 and a mounting bracket 29 made of metal. The mounting bracket 29 is connected to a casing of the equipment connected to the ground. The braid 24 is connected to the equipment casing via the metal collar 26 and the mounting bracket 29, thereby achieving a shielding conduction, and electromagnetic waves, generated from the shielded wire 20, are absorbed by a shielding conduction path. Molten resins are injected to cover a shield connecting portion of the braid 24, thereby forming an inner covering molded portion 28A and an outer covering molded portion 28B by a two-color molding method. In this manner, the electric connector, having the electromagnetic shielding structure, is formed.
The electromagnetic shielding structures of the electric connectors, shown respectively in Patent Literature 1 and FIG. 15, have the following problems.
First, in the case of the related structure of FIG. 14 disclosed in Patent Literature 1, the metal net 8 (which is a cumbersome connecting member) is used to electrically connect the braid 6 to the metal shell 1 for shielding purposes, and this metal net 8 is pressed against the metal shell 1 by the use of the heat-shrinkable tube 9. The number of the expensive component members, including the metal net 8 and the heat-shrinkable tube 9, increases, and therefore this is disadvantageous from the viewpoint of the cost. And besides, the force for sufficiently pressing the metal net 8 against the metal shell 1 can not be obtained only by the heat-shrinking force of the heat-shrinkable tube 9. Therefore, a shielding resistance is unstable, so that the effective electromagnetic shielding can not be effected, and therefore the reliability of the shielding-purpose connection of the braid 6 to the metal shell 1 is affected. In addition, if the heat-shrinkable tube should be damaged or ruptured, the metal net 8 is displaced out of position, and fails to serve to interconnect the metal shell 1 and the braid 6, thus causing electrical disconnection, and this leads to a possibility that the intended electromagnetic shielding function is adversely affected.
In the case of the structure of FIG. 15, in order to connect the braid 24 of the shielded wire 20 to the equipment casing or the like, the metal collar 26 and the metal mounting bracket 29 are used as the relay members for the shielding-purpose connection. And besides, after the braid 24 is connected to the mounting bracket 29, the inner and outer covering molded portions 28A and 28B are formed. Namely, the number of the component members is large, and besides the production process up to the molding step is very complicated, and naturally the production cost increases. In addition, the covering molded portions 28A and 28B adhere to the sheath 23 and insulator 22 of the shielded wire 20 which are molded of different resin materials, respectively, and further adhere to the metal collar 26 and the metal mounting bracket 29. In view of physical properties, it is difficult to think that when a layer, adhering to resins of different natures or metals of different natures, is molded by the use of the same resin, a sufficient adhesion is obtained in an interface, and thus there is encountered a structural problem.
A further problem which is common to the structure of FIG. 14 (disclosed in Patent Literature 1) and the structure of FIG. 15 is that the conductor and the metal terminal are exposed, and a waterproof ability for preventing the intrusion of rain water from the exterior and an oil leakage prevention ability for preventing the leakage of oils (such as lubricating oil used in the equipment) to the exterior are not taken into consideration. Particularly in the case of the latter structure shown in FIG. 15, there is a fear that oil, such as lubricating oil used in the equipment, leaks to the exterior via the conductor 21 of the distal end portion of the shielded wire 20 and the metal terminal 25, and adversely affects other equipment. In the case of the molded electric connector, the durability for a change of properties upon deposition of rain water is different from the durability for a change of properties upon deposition of oil, and the resin material of an ordinary nature, forming the covering molded portions 28A and 28B, can not meet such required characteristics for water and oil.
It is therefore an object of this invention to provide an electromagnetic shielding structure with an oilproof and waterproof ability which achieves a satisfactory shielding performance particularly against electromagnetic waves from an installed large-current/high-voltage cable at low costs, and also has a required oilproof and waterproof performance against rain water and oils.
In order to achieve the above object, according to the present invention, there is provided an electromagnetic shielding structure, comprising:
a sheath wire, having a conductive wire and an insulative sheath covering the conductive wire;
a terminal fitting, clamping the conductive wire exposed from the insulative sheath, and the terminal fitting passing through a conductive mounting member connected to ground;
a molding member, molding so as to cover the sheath wire, the exposed conductive wire and the terminal fitting, and having a first recess and a second recess;
wherein the first recess is formed on a first end portion of the molding member, the first end portion contacting the sheath wire;
wherein the second recess is formed on a second end portion of the molding member, the second end portion contacting the terminal fitting;
a conductive braid, having a tubular shape, and covering the sheath wire and the molding member for absorbing an electromagnetic wave generated from the conductive wire;
a first sealing portion, provided in the first recess so as to adhere the molding member and the insulative sheath for securing a waterproof performance;
a second sealing portion, provided in the second recess so as to adhere the molding member and the terminal fitting for securing an oil proof and waterproof performance; and
a conductive shell, covering the molding member so that the conductive braid is electrically connected to the conductive mounting member.
Preferably, a end portion of the conductive braid and the conductive shell are mounted on the mounting member by a bolt.
Preferably, the first sealing portion is formed by filing a melted resin into the first recess.
Preferably, the second sealing portion is formed by filing a melted resin into the second recess.
In the above construction, the braid, covering the wire, and the conductive shell (such for example as a metal cover) are fastened together by the fastening bolts, and are connected to the conductive mounting member (such for example as a motor outer plate casing), thereby connecting the braid to the ground. Therefore, electromagnetic waves, generated from the wire, can be positively absorbed by the inexpensive connecting structure, thus obtaining the required electromagnetic shielding function. In the covering molded portion which covers and protects the conductor at the wire end portion and the metal terminal press-fastened to this conductor, the first sealing portion is provided in the first recess formed in that side of the molded body contacting the insulator at the wire end portion. Therefore, rain water or the like, intruding along the exposed conductor at the wire end portion, is intercepted, thereby securing the required waterproof performance. And besides, the second sealing portion is provided in the second recess formed in that side of the molded body disposed close to the connection portion of the metal terminal, and therefore oil, such as lubricating oil used in the equipment (e.g. the motor outer plate casing), and water drops are prevented from leaking to the exterior along the metal terminal, thereby securing the required oilproof and waterproof performance.
The first sealing portion of an arbitrary shape can be post-provided in the first recess in accordance to an outer diameter of the wire or others, and the oilproof and first sealing portion of an arbitrary shape can be post-provided in the second recess in accordance with a shape of the metal terminal.
In the above construction, the first and second seal member-mounting recesses are beforehand formed in the molded body, and therefore in accordance with the outer diameter of the wire and the shape and kind of the metal terminal, the suitable resins are poured respectively into the first and second recesses at a later stage, so that the first sealing portion and the second sealing portion can be post-molded. Therefore, this construction can easily meet the use of the inexpensive wire and metal terminal or the use of the expensive wire and metal terminal, thus achieving the enhanced general-purpose ability.
Instead of the first sealing portion and the second sealing portion formed by pouring the resins, for example, tubular packing-like members, molded of elastic rubber, can be post-fitted in the first sealing portion and the second sealing portion, respectively.
According to the present invention, there is also provided an electromagnetic shielding structure, comprising:
a sheath wire, having a conductive wire and an insulative sheath covering the conductive wire;
a terminal fitting, clamping the conductive wire exposed from the insulative sheath, and the terminal fitting passing through a conductive mounting member connected to ground;
a grommet, covering the sheath wire and the terminal fitting, and having a first end portion and a second end portion, the first end portion being closely contact with the insulative sheath;
a conductive braid, having a tubular shape, and covering the sheath wire and the grommet for absorbing an electromagnetic wave generated from the conductive wire;
a housing, formed with a recess at a distal end side of the terminal fitting, the housing fitting the terminal fitting, and being closely contact with the second end portion of the grommet;
a sealing portion, provided in the recess so as to adhere the housing and the terminal fitting for securing an oil proof and waterproof performance;
a conductive shell, covering the molding member and the grommet; and
a shield stopper, fixedly secured to the conductive shell, and holding the housing in the conductive shell.
In the above construction, the satisfactory shielding performance can be obtained at low costs particularly for electromagnetic waves generated from the installed wire carrying large current and high voltage. And besides, the required oilproof and waterproof performance against rain water and oil can be secured.
According to the present invention, there is also provided an electromagnetic shielding structure, comprising:
a sheath wire, having a conductive wire and an insulative sheath covering the conductive wire;
a terminal fitting, clamping the conductive wire exposed from the insulative sheath, and the terminal fitting passing through a conductive mounting member connected to ground;
a grommet, covering the sheath wire and the terminal fitting, and having a first end portion and a second end portion, the first end portion being closely contact with the insulative sheath;
a conductive braid, having a tubular shape, and covering the sheath wire and the grommet for absorbing an electromagnetic wave generated from the conductive wire;
housing, fitting the terminal fitting;
a heat-shrinkable tube, sealing the housing and the terminal fitting, and closely fitted with the second end portion of the grommet;
a conductive shell, covering the housing and the grommet; and
a shield stopper, fixedly secured to the conductive shell, and holding the housing in the conductive shell.
In the above construction, the satisfactory shielding performance can be obtained at low costs particularly for electromagnetic waves generated from the installed wire carrying large current and high voltage. And besides, the required oilproof and waterproof performance against rain water and oil can be secured.